Mobility of Am, Eu and Tc in the presence of humic acids

The impact of the radionuclides on the environment is the subject of intensive studies to determine their toxicity. The speciation forms of the radionuclides have to be known; their mobility in the biosphere can be assessed in this way. The supports able to increase or decrease the mobility of these toxic elements are of different types: inorganic (roc matrix, oxides) or organic (humic substances). The latter are recognized for their great affinity towards some radionuclides, i.e. actinides, Kim et al. (1989). The present work will try to estimate the sorption rate of three radionuclides (americium, europium and technetium) by humic acids. Actinides (Am) and lanthanides (Eu) have a similar behaviour towards organic matter; on the other hand, comparatively, few studies have been undertaken on technetium. This radionuclides is released in the environment as highly mobile pertechnetate TcO4-; its biological availability is very high and the assessment of radiation dose to man has to be determined. However, when reducing conditions prevail in the soils, the geochemical mobility is in fact much lower than was originally suspected. The aim of this work is to try to assess the behaviour of Tc in oxic and anoxic conditions in order to establish the mobility of Tc in the presence of humic acids. The study is based on two methodologies: a static one (in batch) and a dynamic one (in column), where different parameters can be investigated: length of the incubation, flow rate, amount of humic acid, oxidation state of Tc. (orig.)